Abstract

Paratuberculosis (PTBC) is a chronic inflammation of the intestines of ruminants but it can also strike other species, including primates. Ovine paratuberculosis lesions have been the subject of authoritative observations (Perez et al., 1996). The macroscopic picture shows a thickening and wrinkling of the intestinal mucous membrane, regional lymphangitis and lymphandenopathy, principally found in the terminal part of the ileum but also in the colon, jejunum and duodenum. Histomorphological pictures are characterised by chronic granulomatous enterocolitis, whose typical clinical symptom is the loss of weight due to profuse diarrhea. The etiological agent of PTBC is the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) (Marek, 1910); its presence gives rise to a persistent infection of the intestinal macrophages which appear foamy, in a small granuloma within the interfollicular-basal area of the Peyer’s plaques of the ileal tract. In some cases, even in the presence of marked lesions and clear, clinical symptomatology, coloration of the Ziehl-Nielsen (ZN) produces a negative result. DNA analysis of MAP has identified a peculiar insertion sequence, IS900, present in 15–20 pairs per genome (Green et al., 1989).